Description labels disappear as I scroll on my UITableViewController - ios

Question

THE CODE:
ViewController.m
#interface ViewController ()
#property (strong,nonatomic) NSMutableArray<NSString *> *sections;
#property (strong,nonatomic) NSMutableArray<NSMutableArray<TableItem *> *> *items;
#property (strong,nonatomic) NSMutableArray<TableItem *> *sectionItems;
#end
...
- (NSInteger) numberOfSectionsInTableView: (UITableView *) tableView {
return _items.count;
}
- (NSString *) tableView: (UITableView *) tableView titleForHeaderInSection:(NSInteger) section {
NSLog(_sections[section]);
return _sections[section];
}
-(NSInteger) tableView: (UITableView *) tableView numberOfRowsInSection:(NSInteger)section {
return _items[section].count;
}
- (UITableViewCell *) tableView: (UITableView *) tableView cellForRowAtIndexPath: (NSIndexPath *) indexPath {
UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:#"Cell" forIndexPath:indexPath ];
TableItem *item = _items[indexPath.section][indexPath.row];
cell.textLabel.text = item.title;
cell.detailTextLabel.text = item.theDescription;
return cell;
}
All appears as it should. When I scroll down and back up, the description labels have disappeared.
Some context:
TableItem.h
#interface TableItem : NSObject
#property (weak,nonatomic) NSString *title;
#property (weak,nonatomic) NSString *theDescription;
-(instancetype) initWithTitle: (NSString *) title theDescription: (NSString *) theDescription;
#end
It seems to be a problem with dequeueReusableCell. I know this has been asked before, but I checked all I could find and found no answer to my issue.

Answer 1

Possibly, the problem lies in TableItem properties. They are weak, which means actual strings can be freed and nilled at any moment.
So, by the time you scroll up and down, title and theDescription are already nils.
Change your TableItem class:
#property (strong, nonatomic) NSString *title;
#property (strong, nonatomic) NSString *theDescription;
Or, if you want to be sure that after assigning new value to its properties, these values can't be modified, use copy:
#property (copy, nonatomic) NSString *title;
#property (copy, nonatomic) NSString *theDescription;